ladder-back vs backrest

ladder-back and backrest both are nouns.

Word	Noun	Adjective	Verb	Adverb
ladder-back	Yes	No	No	No
backrest	Yes	No	No	No

As nouns, backrest is a hypernym of ladder-back; that is, backrest is a word with a broader meaning than ladder-back:

ladder-back: the backrest of a chair that consists of two uprights with connecting slats
backrest: a support that you can lean against while sitting

Other hypernyms of ladder-back include back.

ladder-back (noun)	backrest (noun)
the backrest of a chair that consists of two uprights with connecting slats	a support that you can lean against while sitting
a chair with a ladder-back